The UK's gender pay gap — the difference in how much men and women are paid hourly on average — rose from 19.7% in 2014 to 20.8% in 2015, the biggest increase of any Europe's main economies.

The latest figures show the UK's gap was bigger than the EU's average pay gap, which stood at 16.3%, and the UK performed fifth worst for gender pay equality of all the major European economies. Germany was third worst, at 22% in 2015, while the Czech Republic's gap was about 23% and Estonia's was about 26%.

According to EU figures, the gap is equivalent to women continuing to work for the remainder of the year but not being paid after early November.

"It is an unacceptable and shocking injustice that women in 21st century Europe work two months a year for free," Vera Jourova, EU commissioner for justice, consumers and gender equality, told the Financial Times.

"This gender pay gap has remained the same for many years — it is still very similar to in 1995," she said.

The EU's gender pay gap was about 25% in 1995. Although it has improved since this, progress has been slow in many countries, and men continue to dominate highly-paid and senior roles.

When the measurement takes additional elements into account, such as hours worked and career breaks for women, the EU-wide gap stands at 39.6%, and the UK's gap stands at 45%. According to European Commission figures, only 6% of chief executives in the EU are women.